This invention relates to a multi-media mailing system which includes a plurality of mail centers in a network and handles signals such as facsimile signals, audio signals and text signals.
Conventional multi-media mailing systems adopt either the single-center configuration or the multi-center configuration. In a multi-media mailing system of the single-center configuration, as shown in FIG. 18, services to terminals 2 of a plurality of switching networks 3 are processed by a single mailing center 1.
Meanwhile, in a multi-media mailing system of the multi-center configuration, as shown in FIG. 19, services to terminals 2 of each of a plurality of switching networks 3 are processed by a mailing center 1 provided for each of the switching networks 3, and information is communicated between each two mailing centers 1 by way of a communication line for exclusive use. In other words, in a system of the multi-center configuration, one mailing center 1 is provided for each switching network 3 so as to disperse the load applied to each mailing center 1.
In a multi-media mailing system of the multi-center configuration, as an information management system by which same information can be obtained from whichever one of the centers information of, for example, a bulletin board is accessed, one of two types including a centralized management type and a decentralized management type is adopted.
A system of the centralized management type will be described first. A system of the centralized management type includes, as seen from the system including broken line representations in FIG. 19, a single management center 50 which obtains information from any of the mail centers 1 by accessing from it and manages information from all of the centers 1 in a centralized condition by itself.
In the system of the centralized management type having such management center 50, information obtained at each of the centers 1 is transmitted to the management center 50, in which the information is managed in a centralized condition. Then, when the management center 50 is accessed from any of the centers 1, particular information is supplied from the management center 50 to the accessing center 1.
On the other hand, in another system of the decentralized management type, as seen from the system which does not include the broken line representations in FIG. 19, information registered in any of the centers 1 is transmitted to any other center 1 so that it may be registered into each center 1.
In the system of the decentralized management type of the construction just described, since information is held commonly by all of the centers, even if one of the centers enters an inoperative condition, no influence is had on operation of any other center.
The conventional multi-media mailing systems of the constructions described above, however, have a subject to be solved, where they are of the single-center configuration, in that the load is concentrated upon the single mailing center, which deteriorates the processing capacitance of the mailing center since processing of all of the terminals 2 of the switching networks 3 is handled by the single mailing center.
Further, where the conventional multi-media mailing systems of the single center configuration are of the single-center configuration, they have another subject to be solved in that, since only one mailing center is involved, if the mailing center is put into an inoperative condition by some reason, then all of the terminals 2 of the networks are put into a condition wherein they do not accept any service.
On the other hand, even where the conventional multi-media mailing systems are of the multi-center configuration and of the centralized management type, they have a subject to be solved in that, if the management center is put into an inoperative condition by some reason, then even if the remaining centers have no trouble, the centers of the entire network are put into a condition wherein they cannot operate at all.
Further, where the conventional multi-media mailing systems are of the multi-center configuration and of the decentralized management type, the order of registration may not be identical between the centers due to a delay in transmission between the centers, and in this instance, the contents of the management tables of the centers may not coincide with each other. Accordingly, they have a subject to be solved in that processing of deletion and updating can be performed only in each of the centers itself.
The conventional multi-media mailing systems of the decentralized management type also have another subject to be solved in that, since subscriber information is different among different centers, a subscriber cannot access any center in which the subscriber is not registered.